Varnish, sludge, rust and corrosion seriously reduce the efficiency of an internal combustion engine by clogging restricted openings and reducing the clearance of moving parts. A high-quality motor lubricating oil must incorporate detergents capable of controlling varnish formation and corrosion. This function has heretofore been mainly performed by certain metallo-organic salts and bases in the lubricating composition. However, the present trend to unleaded fuels and ashless lubricating compositions brought about by certain important environmental concerns necessitates the search for non-metallic (ashless) substitutes for the metallo-organic detergents. These non-metallics must fulfill a host of requirements, primary among which are basicity and thermal stability.